Waste litter heater

ABSTRACT

An automatic biomass fuel burning heating device and method comprising a burn chamber having a sloped floor and a feed auger supplying biomass fuel to be burned. A burn chamber having a feed auger opening in a burn chamber wall. An ash auger to carry ash away from a base of said sloped floor and a heat exchanger carries supply air through the burn chamber to heat a space such as a brooder house. A fan drives supply air through the heat exchanger and a control regulates the speed of the fan and the operation of the feed auger. The control maintain supply air into the brooder house at a constant set temperature by varying the volume rate of air flow based on air inlet temperature and the temperature in the burn chamber.

RELATED APPLICATIONS

This application claims priority under 35 USC 119 to provisional application 60/674,893.

BACKGROUND OF THE INVENTION

In the poultry industry it is common practice to confine a large number of birds in brooder houses. Birds are raised from hatchlings to adults. The process uses litter which acts as bedding for the birds. Litter can be a variety of material including dry saw dust, wood shavings, rice hulls and a variety of other organic materials. A common problem in the industry is what to do with the used litter.

Used poultry litter is typically collected and is often spread over fields. Nominally the used litter can serve as a fertilizer, but spreading used litter on fields releases tremendous amounts of ammonia creating a smell that offends anyone downwind. The spreading of litter is really spreading raw sewage and this leads to runoff that can pollute local streams. Phosphate contained in the litter is also a contaminant that builds up and is then released slowly causing a run-off problem that pollutes streams. Legislation or actions controlling the practice has either been considered or has been enacted by federal and state agencies.

Brooder houses must also be kept warm. Typically propane heat is used. When chicks are young, ideal brooder house temperatures are near 90 degrees Fahrenheit. It is desirable to maintain a warm environment, otherwise young birds will die from the cold or will burn fat to stay warm and this will slow the growth of the older birds. It is desirable to maximize the growth of birds to optimize profitability of the operation.

U.S. Pat. No. 6,244,196 discloses one prior art waste burner device. A fluidized bed as disclosed will tend to form “Clinkers” and is only feasible for large systems such as power plants and would not be economically feasible for an owner of a few brooder houses. A clinker is a solid mass of unburnable material that may also contain fuel that burns on the outside and then tends to clog up the system. Clinkers can form due to silica in rice hulls and dirt which cannot burn for example. Thus this patent cannot operate for long periods of time without someone to tend to it. In brooder house operation, the owner/operator often has a day job to supplement the income from the brooder house, so there is a need for reliable heating that can operate on automatic for hours and even days at a time.

U.S. Pat. No. 4,504,011 shows an LP gas system to heat a brooder house. Gas is convenient but expensive. The '011 patent is a direct fired system, meaning the products of combustion enter the heated space. This is common in the poultry industry as it maximizes energy efficiency. A problem with direct fire is that burning typically creates water as a product of combustion. With propane nearly 0.8 gallons of water enters the building for each gallon of propane burned. When you add water to litter ammonia is released, the release of ammonia is one of the biggest problems for brooder house operators.

Thus it can be seen that there is a need for a system that provides heat for brooder houses at a minimum cost. There is a need to minimize moisture in the brooder houses to minimize ammonia release. Further there is a need to find use for the waste litter generated in brooder houses.

SUMMARY OF THE INVENTION

The present invention provides an automatic waste burning heating device comprising a burn chamber having a sloped floor. An auger supplies waste/biomass fuel to be burned to the burn chamber through an opening in a burn chamber wall. Waste/biomass fuel can include waste poultry litter such as wood fines, rice hulls or saw dust for example. An ash auger carries ash away from a base of the sloped floor constantly during operation of the heating device. A heat exchanger carries supply air through the device to heat a brooder house. A fan moves supply air through the heat exchanger, a control maintains a speed of the supply air fan. The fan supplies outside air through the heat exchanger. This outside air is heated to a nearly constant temperature set by the operator and is blown into the brooder house. The automatic control system varies the amount of outside air being supplied to maintain a constant preset temperature of the air entering the building.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of the device;

FIG. 2 shows a control diagram;

FIG. 3 shows a partial cut away view of the device in use;

FIG. 4 shows the startup control sequence of the device; and

FIG. 5 shows the automatic control sequence of the device

DETAILED DESCRIPTION OF THE DEVICE

FIG. 1 shows a block diagram of the biomass burning heating device 10 in use. The heating device 10 can use a variety of biomass fuel sources including sawdust, wood shavings, rice hulls, or other bio-mass and would typically burn fuel at a rate of up to 4 pounds per minute though larger units are also possible. Typically the biomass fuel has been used as animal bedding or poultry litter adding animal waste as at least part of the biomass fuel. A burn chamber 100 receives used litter L from an auger 110. The auger 110 can receive a flow of litter L from a storage hopper 120. The screen hopper 130 can be used to size the particles of litter L, preventing larger clumps from entering the auger 110. The litter L can be pre screened to remove large clumps prior to being placed in the storage hopper 120 which can include an agitator 125 and vibrator 135 or other mechanical device to assist the flow of litter to the auger 110.

The litter L enters the burn chamber 100 and can be fed onto an incline 150. The angle A of the incline can be such that as litter L burns it will tend to roll down the incline 150. Through experimentation it has been found that an incline angle A can be adjusted such that litter burns as in moves down the incline 150 and such that as litter L reaches the bottom of the incline 150 it will be reduced to ash 160 that can be removed from the burn chamber 100 using auger 170. The ash 160 removed is useful as a fertilizer, the ash can be spread on a field without the environmental concerns associated with raw litter waste.

The burn chamber 100 can include a heat exchanger 200. A fan 210 can blow or move supply air from the outdoors through an inlet 220 and through the heat exchanger 200. The inlet supply air can pass through the heat exchanger 200 picking up heat from the burn chamber 100 and the supply air can be vented from an outlet 230 into the interior space of the building such as a brooder house. The heat exchanger can be of any shape that allows for an efficient exchange of heat and flow of supply air. The inlet 220 can include an inlet supply air temperature sensor 222. Exhaust gasses from the combustion chamber 100 can be expelled into the outdoors through and exhaust 250. Typically the heating device 10 can be contained in a building adjacent the one being heated or in some cases in a building it is heating. For poultry operation, it is desirable to avoid disturbing the birds, and as the hopper 120 would typically be filled using a tractor or fork lift, it is desirable to have the device 10 outside the heated space in a separate structure.

FIG. 2 shows that a control 300 can be used to control the waste/biomass burning heating device 10. The control 300 can sense burn chamber temperature 305 using firebox temperature sensor 102, and sense exhaust temperature 310 at exhaust 250 using exhaust temperature sensor 252 and can sense supply air outlet temperature 315 at outlet 230 using air outlet sensor 232. The control 300 can use the values sensed to control an agitator 125 in storage hopper 120, a vibrator 135 on the storage hopper 120, the feed auger 110, the fan speed 210 and the ash auger 170. The control 300 would typically maintain a firebox temperature 305 between 1150 and 1200 degrees Fahrenheit and an outlet air temperature 315 in a range of 85-95 degrees Fahrenheit for example.

The feed auger 110 typically operates at a speed set for the type of fuel being burned. The speed can be set and changed in the field. For example, the BTU value and burn rate of litter containing rice hulls may differ from litter of wood shavings. However, once the auger 110 speed is set it will not need to be reset so long as the same fuel is used. This allows the device 10 to run automatically for long periods of time. This is very desirable as poultry farm operators often have a job outside the poultry farm, and they need the device 10 to run automatically without the need to constantly tend the fire. If the firebox temperature 305 drops below a set temperature of approximately 800 degrees F. during automatic operation, the control 300 will shut off the feed auger 110 as well as vibrator 135 and agitator 125. If the temperature continues to drop the control 300 can shut off the ash auger 170. The control 300 shuts these off in an effort to rekindle a fire that may have been smothered by too much fuel supply. If the fire fails to restart then the control 300 must be set to manual and the burn chamber 100 must be re-lit. However, if the firebox temperature sensor 305 detects a rise in temperature it can re-start the ash auger 170 and the feed auger 110 and then the agitator 125 and the vibrator 135. The system can run for days without starting to form clinkers which are a problem in many prior art systems. If a small clinker did begin to form it will be carried down the slope 150 and then out of the burn chamber by auger 170.

FIG. 3 shows details of the inside of the burn chamber 100 during operation. The auger 110 presents a slug of litter L at an opening 104 into the burn chamber. The slug of litter L seals the burn chamber 100 and continues to form as new litter is fed into the burn chamber 100 by the auger 110. As the litter L leaves the opening 104 it begins to burn. Combustion air comes from blower 240 and enters from below the slope 150. As the litter L burns it tends to roll down the slope 150 which aids in the complete burning. The slope angle A can be set to yield optimum burn characteristics where the litter fuel will spread out on the slope 150 and burn as gravity, new material and combustion air movement tends to move burning and burnt material down the slope 150 toward the ash auger 170. As the litter reaches the end of the slope 150 it is entirely converted to ash and is carried away by the ash auger 170. Any dirt, silica from rice hulls or other unburnable material also reaches the ash auger 170 and is carried out such that a ‘Clinker’ of unburned or unburnable material will not form. A container, not shown, can store the ash fertilizer prior to spreading it. This ash fertilizer is now water soluble. The nutrients can be absorbed directly into the soil unlike raw litter which must first decay before releasing nutrients.

FIG. 4 shows the system start sequence 400. When there is no fire in the burn chamber 100 a fire can be started manually. The user can bypass the control 300 and manually feed litter L material onto the slope 150 by jogging the auger 110 forward. The user can then light the litter L and close the burn chamber door 106. The user can manually jog the auger 110 forward until the temperature in the burn chamber 100 reaches a preset temperature such as 800 degrees F., or until the exhaust reaches a certain temperature such as 225 degree Fahrenheit then the control 300 switches back to automatic control 500 shown in FIG. 5.

FIG. 5 shows the automatic control sequence 500 of the control 300. The sequence 500 includes a check of output air temp 502 from air temp sensor 232. If the output air temperature is below a set point, such as 90 degrees Fahrenheit for chicks, then the sequence slows 504 the fan 210, reducing the volume of air through the heat exchanger 200 will increase the temperature of output supply air. The sequence 500 checks if firebox temperature 506 is below a set point such as 800 degrees Fahrenheit. A low firebox temperature reading can indicate that too much fuel is being piled onto the slope 150 smothering the fire, so the sequence 500 can trigger a relight mode 510 that can include stopping the feed auger 110 to give the fire a chance to recover. In relight mode 510, if the temperature continues to drop the air fan 210 slows down to maintain the constant pre-set supply air discharge temperature. The combustion air from fan 240 will continue to be supplied. If the fire F failed to light then the control can return to manual start shown in FIG. 4.

If the temperature check 518 indicates a burn chamber temperature above a set point such as 1250 degrees Fahrenheit then the sequence 500 can slow 520 the feed auger 110. If the burn chamber 100 exceeds a high temperature limit the entire heat device 10 will shut down except for the control 300 and the supply air fan 210 until the burn chamber temperature falls below the high temperature limit, then the control will return to the automatic sequence 500. If output supply air check 524 shows the temperature of supply air to be above the set point such as 90 degrees, then the air fan 210 will increase speed 528. If the output supply air temperature exceeds a high temperature limit, control 300 will shut down both augers 110 and 170 and fan 240, agitator 125 and vibrator 135. Only supply air fan 210 will continue to operate. When the supply air at outlet 230 once again drops below the high temperature limit then all items 110,170,240,125 and 135 will automatically restart.

In operation, at start up the combustion air fan 240 is operating, the fan speed or combustion air valve openings 244 can be used to control the rate of combustion air flowing into the combustion chamber 100. The operator can bypass the control 300 which can start litter feeding to the slope 150 from auger 110. The operator can allow the auger 110 to run in bypass mode until about 1 cubic foot of litter L is piled on the slope 150. The operator can then light a fire on top of the pile of litter L for example by lighting a small pile of charcoal on top of the litter L. As the fire starts to burn the heating device 10 will continue to operate in bypass mode with the auger 110 feeding fuel litter L and the combustion air inlet fan 240 supplying combustion air. The door 106 can be closed to allow the temperature within burn chamber 100 to begin to rise. When a preset temperature is reached the operator can switch the heating device 10 from bypass to automatic mode. This switch can occur when the flue gas temperature at sensor 252 reaches a temperature in the range of 215-225 degrees F. for example. The heating device 10 then operates according to the automatic control sequence 500 shown in FIG. 5.

In automatic operation, the rate of fuel feed from auger 110 is set to maintain a desired temperature range within the burn chamber 100, for example an ideal range for many poultry operations is 1150-1200 degrees Fahrenheit. The rate of fuel delivery by the auger 110 can be controlled by manually presetting the speed of the auger 110 for a fuel type and having the auger 110 run constantly. Once set very little adjustment should ever be needed unless the quality or type of fuel changes. As fuel litter L enters the burn chamber 100 most of the burning takes place at the top of slope 150, gravity and the new litter material pushing in will tend to cause the old burning material and ash to slowly roll down the slope 150 until they enter the ash auger 170 which is normally operating constantly. The operation of feed auger 110 and ash auger 170 keeps material moving and is an important aspect to preventing the formation of clinkers. Prior to operation, an operator will have set the temperature that they want supply air from fan 210 to enter the brooder house. For example, with young chicks the desired temperature might be as high as 90-92 degrees Fahrenheit, for older birds the temperature can be lower. Many brooder houses already have a propane or gas fired heat system. The heat device 10 would serve as supplemental heat in these operations. In colder climates an alternate heat source would probably be desired, in warmer southern climates the heat device 10 might be the only source of heat needed for a building. In newly constructed brooder houses the device 10 may also be the sole source of heat.

The litter fuel hopper agitator 125 and screen vibrator 135 can have two adjustments. The first is the time between each run cycle. This can be adjustable for example between 1 to 3 minutes. The second setting is the amount of time that the agitator 125 and vibrator 135 run during each cycle. The normal setting would be that the cycle time would be three minutes and the run time would be 10 seconds. The consistency and type of litter L as well as the moisture content in the fuel are some factors that will determine the times. Over agitation and vibration may cause litter to pack in the storage hopper 120. The purpose of the agitator 125 and screen vibrator 135 is to prevent litter from bridging in the hopper, which would cause the system 10 to run out of fuel prematurely.

Though many specifics are shown there are other variations that could be used without departing from the spirit of the invention. For example, the control sequence 500 could sense the degree of opening of valve 244 of the combustion air inlet 240 and automatically increase the degree of opening to control the rate of supply of combustion air, this valve is current set manually. Also though the auger 110 is shown as running at a constant speed the control 300 could control the speed of the auger or could cycle the auger on and off to control the rate of fuel flow in response to conditions such as fire box temperature. The system could also use an exhaust damper to control burn conditions in the fire box. 

1. An automatic biomass fuel burning heating device comprising; a burn chamber having a sloped floor, a fuel feed supplying biomass fuel to be burned to said burn chamber through an opening; an ash auger to carry ash away from a base of said sloped floor, a heat exchanger carrying supply air through said burn chamber to heat a space, a supply air fan moving said supply air through said heat exchanger; a control controlling said supply air fan and said fuel feed.
 2. The automatic biomass fuel burning heating device of claim 1 wherein said control regulates a speed of said supply fan air in response to a temperature of supply air exiting said heat exchanger.
 3. The automatic biomass fuel burning heating device of claim 1 wherein said biomass fuel is used animal litter.
 4. The automatic biomass fuel burning heating device of claim 1 wherein said biomass fuel is supplied to an upper portion of said sloped floor and moves down said sloped floor toward said auger as it burns.
 5. The automatic biomass fuel burning device of claim 1 wherein said control includes an automatic operation mode wherein said fuel auger runs at a constant speed and wherein said ash auger runs at a constant speed.
 6. The automatic biomass fuel burning device of claim 5 wherein said control includes a manual light mode and an automatic relight mode wherein if said control senses a reduction in firebox temperature it will automatically stop the fuel feed auger.
 7. The automatic biomass fuel burning device of claim 2 wherein said opening is above said sloped floor.
 8. A method of heating a brooder house with supply air including the steps of; supplying an automatic flow of biomass fuel to a fire in a burn chamber; supplying a flow of combustion air to said burn chamber; auguring ash away from said burn chamber as said fire is burning; monitoring a temperature of said supply air; controlling flow of supply air through a heat exchanger to maintain a constant supply air temperature.
 9. The method of claim 8 wherein the step of supplying an automatic flow of biomass fuel includes the step of interrupting the flow of biomass fuel if a sensed temperature in said burn chamber fall below a preset level.
 10. The method of claim 9 wherein the step of supplying an automatic flow of biomass fuel includes the further step of interrupting the flow of biomass fuel if the sensed temperature in said burn chamber rises above a preset level.
 11. The method of claim 8 wherein the step of controlling the flow of supply air includes slowing the speed of a supply air fan if the sensed temperature of the supply air falls below a preset limit.
 12. The method of claim 8 wherein the step of supplying an automatic flow of biomass fuel includes the step of auguring fuel from a hopper.
 13. A brooder house heating device comprising; a burn chamber having a sloped burn surface, a fuel feed supplying biomass fuel to be burned to said burn chamber through an opening; an ash auger to carry ash away from a base of said sloped burn surface, a heat exchanger carrying supply air through said burn chamber to heat a space, a supply air fan moving said supply air through said heat exchanger; a control controlling said supply air fan and said fuel feed.
 14. The brooder house heating device of claim 13 wherein said control regulates the speed of said supply fan air in response to a temperature of supply air exiting said heat exchanger to heat said brooder house.
 15. The brooder house heating device of claim 14 wherein said biomass fuel is used litter from said brooder house.
 16. The brooder house heating device of claim 14 wherein said biomass fuel is supplied to an upper portion of said sloped burn surface and moves toward said base as it burns.
 17. The brooder house heating device of claim 16 wherein combustion air is supplied to said burn chamber through said sloped burn surface.
 18. The brooder house heating device of claim 17 wherein said control includes an automatic operation mode wherein said fuel auger runs at a constant speed and wherein said ash auger runs at a constant speed. 